1. Field of the Invention
The present invention relates to a ballast for a fluorescent lamp. More precisely, the present invention relates to a compact L-C ballast having a capacitor in series with a transformer that uses a primary coil and a shorted secondary coil, adapted for use in a low wattage fluorescent lamp.
2. Description of the Prior Art and Related Information
Fluorescent lamps of all types are very popular for use in the home or office because of their high operating efficiency as compared to incandescent lamps. Indeed, fluorescent lamps emit light at several times the efficiency of a typical incandescent lamp. Furthermore, fluorescent lamps do not generate as much heat as a typical incandescent bulb, thereby conserving radiant energy in that respect.
A typical fluorescent lamp is constructed from a glass tube that contains two electrodes at opposite ends, a coating of powdered phosphor covering the interior of the tube, and small amounts of mercury. The electrodes when energized provide a large potential across which free electrons initiate an arc. The radiant energy from the arc contains shortwave ultraviolet energy that is converted into light by the phosphor coating. In this process, the fluorescent effect is caused by the mercury when it is vaporized in the arc.
Furthermore, most fluorescent lamps require a ballast. A ballast is necessary to maintain constant current flow into the lamp. In a ballast resistor, for example, the resistance increases as temperature increases. As resistance increases, less current is allowed through, thus lowering the temperature and consequently lowering the resistance. Current flow is thus maintained at a constant level.
Ballast action for a fluorescent lamp can also be obtained through use of an inductor/capacitor ballast (i.e., L-C ballast). In such a ballast, the capacitor continually charges and discharges while the inductor loads and unloads the circuit, thereby continually regulating current flow to the fluorescent lamp.
In a conventional L-C ballast for a low wattage (e.g., 4 to 8 watt) fluorescent lamp, the inductor typically requires 1200 turns in its coil. Because of the number of turns, power consumption is great and energy is wasted in the inductor when converted to heat. Not only is energy wasted in the conventional ballast, the labor and material required to build an inductor with 1200 turns is accordingly high. Finally, the durability and life expectancy of a lamp running that hot is questionable. Accordingly, there is a need for an efficient operating ballast for a low wattage fluorescent lamp.